I know from working with the disabled community, that most people are not well read on the laws, but they love to toss them around.
And, you are correct, I don't have any autistic children (or other disabilities) in my family, but I also come from a unique perspective. As a child I was the "sickly" one (probably because I was premature), and as a result I was always told how "sick" I was, and eventually, for a period of my life, that became a crux for me as a child (and my family).
I couldn't play sports because I had Asthma, I was always getting in trouble at school because I was Hyperactive (what later became ADHD)...
I'll give you an example...I was around 10 or so when this happened. I was visiting my Grandparents, and they took me out, along with my great grandmother (who had Alzheimers, but it was mild at this point) and my great Aunt) to a Wendy's Superbar. I ordered the "all you can eat" bar. Where I was from (around DC), that meant you got a plate. The "one trip" was a bowl. I was SURE of this! So, I took the plate, and filled it up. I went to get a refill, and...was told that I couldn't! The plate was for the one trips!
I ended up throwing a fit in the middle of Wendy's, one I'm not proud of today, but...it happened. I screamed and cried and cursed out the workers. I also thoroughly embarrassed my family. We left early, and I got my bum tanned that night by my grandmother, but my parents made me feel this was ok. It was due to my "condition" over the phone. So, I self justified this behavior because they did.
It wasn't until I was around 12 or so that some military doctor finally told my parents to stop coddling me and shove me out into the real world. Stop searching for reasons and accommodations, and start looking for solutions.
He had me enroll in soccer, and after a few years of that my asthma largely went away...why? My lungs got stronger and I learned how to manage it. I started doing better in school. Why? Because I couldn't be the "stupid silly kid" who blamed it on some disease I didn't understand, rather I was held accountable.
It sucked for me at the time...but it was the best thing they ever did. Do I have issues? Sure. I'm OCD, I have social interaction issues, I have excuses out the .
But, none of that means I can't wait in a line.
And, then I look at people like Zach Anner.
http://www.youtube.com/user/ZachAnner
Of course, this is nothing close to your brother's condition or experience, so please don't think I'm conflating his life experience because of it. But, it is vastly similar to the "conditions" that are presented as reasons for accommodation. "My child can't wait in line"
The point is, if you make excuses, excuses will rule your life.